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From: BIRCHWAY@aol.com [mailto:BIRCHWAY@aol.com]
Sent: Thursday, October 13, 2005 9:44 PM
To: garyschafer@comcast.net
Subject: Re: [Amps] Dedicated 220AC Wiring for Amps..
I spent 30 years as a broadcast engineer. Power companies and broadcasters
are paranoid about lightning hits and go to great lengths to minimize them.
The power company is only concerned about their own equipment. They care
little about the customer's equipment.
We had a 700 foot tower and
the sections are prepainted on the ground and then erected, so they are
effectively insulated
from each other with paint. Each section had a heavy copper wire to the next
one.
It is standard practice to put a strap around each tower leg joint even if
there is no paint in the joint. Joints have a high resistance compared to
the rest of the tower. Even though that joint resistance may be only a tenth
of an ohm or less. It can have a substantial voltage drop with the high
current of lightning.
there was a 25 square foot copper screen buried at the tower base and
strapped to the tower.
A buried screen does little for lightning dissipation. Length is needed.
2 inch copper strap was buried out to each of the three guy wire bases and
strapped. 2 inch copper strap was incorporated into the concrete of the
building foundation and tied to strap going out to the tower. All as a
counterpoise for lightning.
Many ground rods and a single point ground for all equipment are also needed
for a good lightning ground.
We still had trouble initially, as a hit would take out things like tape
recorder motors, florescent ballasts, i.e. things with a high power factor.
the final solution was to buy some old trolley wire from a junk yard which
was rectangular heavy ribbon. This was buried about two blocks to the city
water system and tied in.
Two blocks distance is much too long to be effective for lightning. If the
water system was tied in or not it probably would have made no difference.
We never had any more problems with the two 25 kw amps going out either.
Lightning will look for the " softest " ground, which could be in your yard
or further down the power line. if you walk down your power line and look up
at the pole, you will see that there is a jumper from the neutral down to a
ground rod at each pole. If a hit happens to get into the pole pig
and can't get to ground, it can boil the oil and blow the housing apart. The
power company engineers are the real pros when it comes to lightning. My 2
cents, sorry about the long post....
Lightning will go to the lowest inductance ground path.
73
Gary K4FMX
Bob...W0PQX since 1945....
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